Influence of blood glucose-related factors to glucose tolerance in acutely ill severe patients evaluated by means of bedside-type artificial pancreas

Purpose

To verify the importance of the role of blood glucose (BG)-related factors to glucose tolerance in acutely ill severe patients with glucose intolerance.

Materials and methods

Thirty-four patients in whom BG levels were controlled by means of a bedside-type artificial pancreas (STG-22; NIKKISO Corporation, Japan) were investigated. The target of BG control by STG-22 was set to 150 mg/dl. Glucose tolerance was evaluated by the following five parameters: M value (mg/kg/min), glucose disposal rate measured by the glucose clamp method (GC) using STG-22; M/I value (ml mg/kg/min/mU), M value divided by the blood insulin level (I), which indicates insulin sensitivity; daily mean BG level (BGm) (mg/dl); I/E ratio, the amount of administered insulin from STG-22 divided by administered energy (glucose) (mU/kcal); and insulin clearance (IC) (ml/kg/min), measured by GC with a two-step insulin infusion rate (IIR). GC was performed with a clamped BG level of 80 mg/dl and IIR of 1.12 and 3.36 mU/kg/min. M1, M3 and I1, I3 indicate the M value and I value when IIR is 1.12 and 3.36, respectively (normal value of M1: 5–10). the first measurement of GC was performed in acute conditions for all the patients, and the second measurement was done 1 week after the first measurement for 20 patients. Organ dysfunction and endogenous insulin production were evaluated by SOFA score and blood C-peptide reactivity (CPR), respectively. Nutritional support for all the patients was performed with total parenteral nutrition. Patients were classified in four groups (A, B, C and D) according to M1 and BGm. Patients with decreased M value (M1 < 5) were subdivided into two groups (A [n = 23], increased BGm, 165 < BGm; B [n = 11], BGm <165). Patients with normal M value (5 < M1) were subdivided into two groups (C [n = 14], BGm <165; D, 165 < BGm).

Results

(1) The BGm and I/E ratio in group A versus group B were 184 ± 15 vs 150 ± 15 and 51 ± 22 vs 24 ± 18 (P < 0.005), respectively. However, there was no significant difference between group A and group B in the amount of administered glucose, SOFA score, M value (M1, M3), M/I value (M1/I1, M3/I3), IC, and CPR. (2) The BGm and I/E ratio in group C versus group D were 142 ± 19 vs 172 ± 12 and 13 ± 11 vs 50 ± 46 (P < 0.01), respectively. However, there was no significant differences between group C and group D in the amount of administered glucose, SOFA score, M value (M1, M3), M/I value (M1/I1, M3/I3), IC, and CPR.

Interpretation

There was discrepancy between the M value and BGm, I/E ratio in group B and group D. The M value was measured under a BG level of 80 mg/dl, while the target of the BG control was set to 150 mg/dl. Therefore, the influence of BG-related factors (BG itself or some factors closely related to BG – ex. function of glucose transporter-2) to glucose tolerance was considered in both group B and group D (increased [decreased] glucose metabolism by those factors in group B [group D]).

Conclusions

BG-related factors seem to have a significant role for glucose tolerance. The artificial pancreas, STG-22, was considered to be useful not only for BG control, but also for further understanding and evaluation of complicated glucose metabolism in acute severely ill patients.